1. Field of the Invention
The present invention relates to a method of enhancing immunogenicity of tumor cells and pathogen-infected cells using a compound having an xcex1-glycosylceramide structure, and more particularly to tumor therapy using tumor cells of which immunogenicity is enhanced.
2. Background Art
In order to treat tumors including melanoma (Mitchell, M. S. et al., J. Clin. Oncol., 8, 409 (1990)), kidney cancer (Neidart, J. A. et al., Cancer, 46, 1128 (1980)), ovarian cancer (Freedman, R. S. et al., Gynecol. Oncol., 29, 337 (1988)), and colon cancer (Hoover, H. C., Cancer, 55, 1236 (1985)), attempts were made to induce tumor-specific immunity in the cancer-bearing hosts by immunizing patients with autologous or allogeneic tumor cells previously inactivated by chemotherapeutic agents or radiation. However, immunogenicity of tumor cells is relatively low different from that of foreign substances such as bacteria because these are originally transformed from host cells. Thus, effectiveness was not as anticipated and only a minor effect was observed in cancers such as melanoma or kidney cancer of which immunogenicity is relatively high (Mullen, C. A. et al., in Cancer Chemotherapy and Biological Response Modifiers, eds. Pinedo, H. M. et al., Elsevier Science B. V.), pp 285-294 (1996)).
Recent developments in molecular biology and genetic engineering made it possible to introduce genes, and it was attempted to apply genetically modified tumor cells expressing cancer-related antigen for cancer therapy. For example, tumor antigen genes were transduced into autologous tumor cells, or otherwise non-self tumor cells if it is difficult to obtain autologous tumor, and obtained tumor cells of which immunogenicity was increased over the original tumor cells were used in tumor therapy. However, at this time, since only a small number of antigens are identified as tumor-related antigens, such attempts are carried out only for limited kinds of cancers (Conry, R. M. et al., Cancer Res., 54, 1164 (1994)). Furthermore, it has been revealed that therapeutic efficacy cannot be attained as anticipated by simply enhancing antigenicity of tumor cells because the immunity of cancer-bearing hosts is often markedly impaired by factors produced by tumor cells, or the like, so that it is rather important to restore the immunity of the cancer-bearing hosts. Consequently, recent studies are mainly focused on attempts to restore the impaired host immunity by immunizing them with cells to which cytokine genes, major histocompatible antigen genes, costimulatory molecules or the like are introduced in order to improve the therapeutic effect. Examples of the tumor cells used in reported studies include those to which cytokine genes such as IL-2 (Connor, J. et al., J. Exp. Med., 177, 1127 (1993)), IL-4 (Golumbek, P. T. et al., Science, 254, 713 (1991)), IL-6 (Porgador, A. et al., Cancer Res., 52, 3679 (1992)), IFN-g (Belldegrun, A. et al., J. Natl. Cancer Inst., 85, 207 (1993)), GM-CSF (Dranoff, G. et al., Proc. Natl. Acad. Sci. USA, 90, 3539 (1993)), IL-12 (Tahara, H. et al., Gene Therapy, 2, 96 (1995)) were introduced, and those to which MHC class II and B7-1 genes (Travis, J. et al., Science, 259, 310 (1993); Basker, S. et al., J. Exp. Med., 181, 619 (1995)) were introduced.
Thus, tumor therapy using tumor cells modified by gene transfer is tested for clinical application all over the world (Roth, J. A. et al., J. Natl. Cancer Inst., 89, 21 (1997). However, gene manipulation for this procedure is complicated (Pardoll, D. M., Immunol. Today, 14, 310 (1993)). Furthermore, vectors which introduce genes efficiently to obtain sufficient therapeutic efficacy have not been developed. Thus, there is a need for further improvement in the tumor therapy described above (Mullen, C. A. et al., in Cancer Chemotherapy and Biological Response Modifiers, eds. Pinedo, H. M. et al. (Elsevier Science B. V.), pp 285-294 (1996).
xcex2-Glycosylceramides, in which various sugars bind to ceramides via a xcex2-bond, can be found in the body (Svennerholm, L. et al., Biochem. Biophys. Acta, 280, 626 (1972); Karlsson, K. et al., Biochem. Biophys. Acta, 316, 317 (1973)). On the other hand, it is known that xcex1-glycosylceramides have marked immunostimulatory activity and antitumor activity (Morita, M. et al., J. Med. Chem., 38, 2176 (1995)). Such activities by xcex1-glycosylceramides are known to be much stronger than those by xcex2-glycosylceramides (Motoki, K. et al., Biol. Pharm. Bull., 18, 1487 (1995)). Furthermore, it is known that compounds having an xcex1-glycosylceramide structure can augment antigen-presenting function of antigen presenting cells, and tumor therapy using the antigen-presenting cells stimulated by compounds having an xcex1-glycosylceramide structure is very effective. It is also known that administration of compounds having an xcex1-glycosylceramide structure protect the body from radiation (Motoki, K. et al., Bioorg. Med. Chem. Lett., 5, 2413 (1995)), and increases the number of platelets and leukocytes (Motoki, K. et al., Biol. Pharm. Bull., 19, 952 (1996)).
However, as far as the present inventors know, there is no report that tumor cells treated with xcex1-glycosylceramides are useful in tumor therapy and that xcex1-glycosylceramides enhance immunogenicity of tumor cells.
The present inventors have now found that tumor cells which were cultured in vitro in a medium containing a compound having an xcex1-glycosylceramide structure showed high immunogenicity, that a marked antitumor effect was observed by administrating the cells above or the cells modified by radiation to cancer-bearing animals, and that the cells were highly safe in tumor therapy because their tumorigenicity is lost. The present invention is based on these findings.
An objective of the present invention is to provide a composition for enhancing immunogenicity of tumor cells, by which the tumor cells effective for tumor therapy can be readily prepared; a composition for enhancing immunogenicity of pathogen-infected cells, by which pathogen-infected cells effective for the treatment of infectious diseases or the like can be readily prepared; a method for enhancing immunogenicity of cells; cells of which immunogenicity is enhanced by an xcex1-glycosylceramide; a pharmaceutical composition comprising the cells above for the treatment of diseases, particularly tumors, associated with the cells; use of the cells for the manufacture of the pharmaceutical composition, and a method for the treatment of diseases, particularly tumors, associated with the cells.
A composition for enhancing immunogenicity of tumor cells or pathogen-infected cells according to the present invention comprises a compound of formula (I): 
wherein
R1 represents H or OH,
X represents an integer between 7 and 27,
R2 represents a substituent selected from the group consisting of the following (a) to (e) (wherein Y represents an integer between 5 and 17):
(a) xe2x80x94CH2(CH2)YCH3 
(b) xe2x80x94CH(OH)(CH2)YCH3 
(c) xe2x80x94CH(OH)(CH2)YCH(CH3)2 
(d) xe2x80x94CHxe2x95x90CH(CH2)YCH3 
(e) xe2x80x94CH(OH)(CH2)YCH(CH3)CH2CH3, and
R3 to R9 represent substituents as defined in any one of the following i) and ii):
i) when R3, R6 and R8 represent H,
R4 represents H, OH, NH2, NHCOCH3, or a substituent selected from the group consisting of the following groups (A) to (D): 
R5 represents OH or a substituent selected from the group consisting of the following groups (E) and (F): 
R7 represents OH or a substituent selected from the group consisting of the following groups (A) to (D): 
R9 represents H, CH3, CH2OH or a substituent selected from the group consisting of the following groups (Axe2x80x2) to (Dxe2x80x2): 
ii) when R3, R6 and R7 represent H,
R4 represents H, OH, NH2, NHCOCH3, or a substituent selected from the group consisting of the following groups (A) to (D): 
R5 represents OH or a substituent selected from the group consisting of groups (E) and (F): 
R8 represents OH or a substituent selected from the group consisting of the following groups (A) to (D): 
R9 represents H, CH3, CH2OH or a substituent selected from the group consisting of the following groups (Axe2x80x2) to (Dxe2x80x2): 
or a salt or solvate thereof.